1. Field of the Invention
The present invention relates to a method of and a system for work transportation control and, more particularly, to a method of and a system for controlling a work handling apparatus to transport works onto a work transportation line.
2. Description of Related Art
It has been widely popular for a long time in so-called production lines, such as automobile production or assembly lines, to use work handling apparatuses or robots to automatically load a transportation conveyer with blanks or finished components, such as cylinder blocks, transmission cases and the like, for transportation to a work station. The work handling apparatus holds works placed on a stack of work pallets at a work store and loads the belt conveyer with one work after another. Such an automatic work handling system is known from, for instance, Japanese Unexamined Patent Publications No. 61-55016, 2-180573 or 3-95025.
A work transportation control system controls a work handling apparatus of this kind to handle works at timed intervals. Since the works are not always placed in the same positions on the pallets, it is necessary to automate and simplify, as far as possible, positioning of the work handling apparatus relative to these works. In order to provide for an optimum utilization of the work handling apparatus, the work transportation control system is provided with a means for detecting work positions.
One of the approaches to position detection is to use electronic image analysis to recognize the position of a work based on a distribution pattern of picture elements of a two-valued image to which a many-valued image of the work is electronically transformed. Specifically, an image is broken with a threshold level into dark and bright picture elements and these dark and bright picture elements are numerically valued at zero (0) and one (1), respectively. This teaching alludes to generalized techniques for assuring consistant position detection of works.
There have also been known work handling apparatuses having a pair of work handling units for handling shafts or spindles including holding means which are adjustable according to lengths or diameters of these shafts or spindles. Such a work handling apparatus is known from, for instance, Japanese Unexamined Utility Model Publication No. 5-26281.
While the work transportation control system may have advantages over the prior art, nevertheless, various constraints must be imposed upon the number of work types which are different in standards, dimensions, shapes and/or attributes. In so-called multi-kind small quantity production lines, where different types of productions such as, for instance, automobile cylinder blocks having different numbers of cylinders or different distances between adjacent cylinders are assembled, it is necessary to permit changing and/or readjusting of a work handling tool and altering of an operation of the work handling tool according to replacement of one type of works with another. This is known as "rearrangement" . Rearrangement is an irritating manual operation which follows an alteration of work type. In the course of increasing both automation of multi-kind small quantity production lines and production efficiency, it is necessary to automate and simplify rearrangement as far as possible.